diff_parse: free object instead of its pointer In e7330016a (diff_parse: check return value of `git_diff_init_options`, 2017-03-20), we've introduced an error check whether we're able to correctly initialize the diff options. This simple commit actually introduced a segfault in that we now try to free the pointer to the allocated diff in an error case, instead of the allocated diff itself. This commit fixes the issue.